Rotor construction



Jam. 39, 1%45. 5 J GORAN 2,363,296

ROTOR CONSTRUCTION Filed Oct. 29, 1945 2 Sheets-Sheet 1 512 mm 50mm QWMj. 3@, 5 J ORAN ROTOR CONSTRUCTIQN Filed Oct. 29, 1943 2 sheets -sheet 2QFMW 5/2 1 4 27 J 50mm i atenteel can. 3% 39th PATENT osric Steven J.Goran, Milwaukee, Wis., assignmto The Louis Allis Qompany, Milwaukee,Via, a I corporation oi Wisconsin Application October 29, 1943, SerialNo. 508,111

3 Claims.

This invention relates to the manufacture of squirrel case rotors forelectric motors and refers particularly to rotors of the cast type as inthe oopending applicationoi Steven J. Goran, Serial No. 458,258, filedSeptember 14, 1942, of which this application is a continuation in part.

It is the purpose of this invention to provide an inexpensive practicalmanner of insuring the formation of radial ventilating passages in thefinished rotor through the use of temporary spacers between groups oflaminations, the spacers being made of a material easily destroyed orremoved by treatment which does not efiect the cast rotor bars or thelaminations.

In the aforesaid pending application, the spacers were defined as beingmade of any suitable destroyable material and cardboard was specificallydisclosed as an example. In that case the rotor, after the castingoperation, was baked at a temperature high enough to carbonize thecardboard but not melt the cast metal so that the spacers could beremoved by an air blast.

With the use of spacers formed of cardboard or similar material when thehot molten metal strikes the edges of the slots punched into theperiphery of the spacer some of the spacer material is burned away andas a consequence the metal being cast flows between the groups oiiaminations to form spacing projections therebe tween.

While this method has proved generally satisfactory the presentinvention seeks to further reduce the cost of the process bysubstituting a spacer formed of material which can be reused after it isremoved from the finished rotor.

For instance, a tin alloy, which melts at a tam perature considerablylower than the melting point of the aluminum from which the rotor barsare cast, would be a very practical material, but

other materials can be used as will be pointed out hereinafter.

With a view toward further reduction in the cost of manufacture, thisinvention has as another of its objects the provision of a spacer whichhas peripheral notches for alignment with the punched slots of thelaminations with the notches larger than the slots to define pockets forthe reception of the molten metal in the casting of the rotor. in thismanner the desired spacing projections are formed on the bars but withthe advantage of having the projections all alike and of definite shapeand size. L

With the above and other objects in view whic will appear as thedescription proceeds, this invention resides in the novel construction,combina tion and arrangement of parts substantially as hereinafterdescribed, and more particularly defined by the appended claims, itbeing understood that such changes in the precise embodiment of thehereindisclosed invention may be made as come within the scope of theclaims.

The accompanying drawings illustrate one complete example of thephysical mbodiment of the invention constructed in accordance with thebest mode so far devised for the practical application of the principlesthereof, and in which:

Figure 1 is a perspective view of a rotor constructed in accordance withthis invention and having parts thereof broken away and in section;

Figure 2 is a perspective view of a few of the rotor laminations and oneof the spacers to show their relative configurations;

Figure 3 is a cross-sectional view through the casting mold illustratingthe manner in which the rotor is cast; and

Figure 4 is an enlarged fragmentary detail view illustrating the spacingprojections formed integrally with the rotor bars during the casting ofthe rotors.

Referring now particularly to the accompanying drawings, in which likenumerals refer to like parts, the numeral 5 designates the rotorlaminations which are punched from thin sheets of steel or othersuitable" material and which are held assembled between end rings 8 by aseries of rotor bars '5 cast integrally with the end rings.

The laminations are punched to provide a bore a for the reception of therotor shaft 9 and to also provide longitudinal air passages l0. Thesepassages communicate with radial ventilating passages i between groupsof laminations. It-is the formation of these radial ventilating passageswith which this invention is chiefly concerned.

inasmuch as the rotor bars and end rings are cast, it follows that toprovide the radial ventilating passages, temporary spacers must beinserted between laminations where the ventilating passages are to belocated. To this end, ringlike spacers i2 are provided.

These spacers are of the same diameter as the laminatlons and areinserted between groups of v laminations during their assemblypreparatory to casting. Notohes i3 opening to the periphery of thespacers are so spaced as to align with the bar forming slots l4 punchedinto the peripheral.

portions of the laminations. The notches I3, however, are larger thanthe slots. so that when the rotor bars are cast, spacing projectionsi5'of definite size and shape will be formed on the rotor bar -to spacethe groups of laminations around the periphery of the rotor. .At thecenter permanent spacing collars I6 of suitable metal are providedbetween the groups of laminations. These collars, together with thespacing lugs or projections l5, firmly hold the groups of laminationsproperly spaced.

In preparing the rotor for the casting operation the laminations andspacer are assembled on a suitable mandrel ll in the manner well knownin the art and clamped between upper and lower heads iii and 59,respectively. The assembly is then mounted in a casting press with thelower head serving as a plunger and entering the pot of the press.

By virtue of th provision of suitable passages 2| and 22 in the headsthe molten fluid 23 is forced up into the rotor bar and end ring formingspaces as the ram of the press descends. It is, of course, understoodthat the open slot are closed by a removable sheath 24 during thecasting operation.

After the casting operation the entire rotor is treated to either meltor dissolve the temporary spacers l2 depending upon the material fromwhich they are made.

As indicated hereinbefore, tin alloys which melt at temperatures wellbelow the melting point of aluminum are suitable where the spacer ito'be made of metal. Many other materials, however, are suitable.

For instance, plastics which will dissolve upon treatment with aninexpensive solvent that has no effect upon the cast rotor can beemployed. Also it is possible to use clay or similar material, thebinder of which can be readily dissolved.

In any event, it is desirable to employ a material which can beliquified and subsequently reused by pouring the same into a mold shapedto form the spacer.

In this way a double saving is effected for not only is the materialused for the spacer saved, but molding the spacer is considerablycheaper than punching it from a blank.

From the foregoing description, taken in connection with theaccompanying drawings, it will be readily apparent to those skilled inthe art that this invention provides an exceedingly simple andinexpensive method of providing case squirrel cage rotors with radialventilating passages.

What I claim as my invention is: 1. The hereindescribed method of makingsquirrel cage rotors having cast conductor bars embedded in the alignedslots of a stack of punched laminations which comprises; assembling thelaminations with a temporary spacer of solid material capable of beingliquefied by a treatment which does not affect the metal of which therotor is cast or the laminations, and with the spacer extending to theperiphery of the laminations but provided with notches in line with theslots of the laminations but larger than the slots so that in castingthe bars the metal filling said notches forms lug-like projections tospace the groups of laminations between which the spacer is interposed;casting the conductor bars; and subsequently liquifying the spacer toremove the same and leave radial ventilating passage between theconductor bars and said groups of laminations.

'2. The hereindescribed method of making a squirrel cage rotor havingcast conductor bars embedded in slots in a laminated core whichcomprises: assembling the laminations of the core with their slotsproperly aligned and with the laminations divided into at least twogroups held spaced apart by a spacer of metal having a melt ing pointlower than that of the metal of which the conductor bars are cast, andwhich spacer has peripheral notches in line with the slots of thelaminations but larger than the slots so that the metal 'of theconductor bars flowing into said notches form uniform lug-likeprojections of definite size and shape to hold the two groups oflaminations spaced apart at the periphery of the rotor; casting theconductor bars into the slots and notches; and subjecting the rotorafter the casting operation to a temperature high enough to melt thespacer but not high enough to affect the cast conductor bars.

3. The hereindescribed method of making a squirrel cage rotor havingcast conductor bars embedded in slots in a. laminated core whichcomprises: assembling the laminations of the core with their slotsproperly aligned and with the laminations divided into at least twogroups held spaced apart by a spacer of solid material capable of beingdissolved by a solvent which in nowise affects the cast rotor bars andwhich spacer has peripheral notches in line with the slots of thelaminations but larger than the slots so that and subjecting the rotorafter the casting operation to treatment with a solvent capable ofdissolving the spacer without afl'ecting the cast conductor bars.

STEVEN J. GORAN.

